Increased usage of biopolymers from renewable resources is highly desirable in the current strive in society towards sustainable development. Biopolymers from renewable resources exhibit considerable advantages in terms of for instance reduced carbon dioxide emissions, biodegradation, and reduced toxicity. Wood and polysaccharides such as cellulosic fibers and starch constitute the currently most commonly used polymeric materials from renewable resources. Except for fibrous cellulosics, starch is the most commonly utilized plant-based biological polymer for large-scale industrial applications, such as coatings, adhesives, and packaging. In spite of the commercial and industrial success of starch as a biopolymer, it has several drawbacks such as moisture sensitivity and brittleness. The disadvantages associated with starch relate predominantly to the molecularly mixed starch composition comprising both amylopectin and amylose structures, meaning that intermolecular cohesive interactions and toughness-enhancing physical entanglement are limited. Retrogradation, i.e. increased degree of crystallinity with time, is another problem associated with starch-based plastics. Furthermore, ethical issues have been raised with regards to the use of starch, since major starch sources, such as corn and potato, are also used as food.
Starch can converted into ‘thermoplastic’ starch (TPS), which is readily processable by a number of commonplace techniques, for instance extrusion, injection molding, and film blowing. Among starch components, amylose shows much better mechanical properties than the brittle amylopectin. Nevertheless, since amylose is always present in plants as a mixture with amylopectin, amylose purification would increase the costs. Since starch and starch blends are becoming widely used in applications such as packaging materials and biocomposites, it is of profound interest to explore alternative water-soluble biopolymers with improved property characteristics from nonfood resources.